Functional membranes in which a polymer obtained by polymerizing monomers having an ion exchange group or various other functional polymer is filled into a porous membrane are used in many applications. For example, there is a fuel cell that is a type of electrochemical device based on an electrolyte membrane in which a polymer electrolyte is filled into a porous membrane. The performance of this fuel cell has been significantly enhanced in recent years by modifications and other improvements in the electrolyte membrane and catalyst technique, and development of such cells for use in low-emission vehicles and the like is progressing. This type of functional membrane is manufactured by impregnating a porous membrane with a functional monomer or the like, and then polymerizing the functional monomer. Methods are known whereby both sides of the porous membrane are covered with a polyester film as a release material during polymerization, and the membrane is heated under pressure in a nitrogen atmosphere (see Patent Document 1, for example).
Patent Document 1: JP-A-11-335473